The present invention relates to innovations and improvements in axle suspensions for trucks and trailers and in certain components of such systems. More particularly, the present invention relates to suspensions wherein a uniquely designed leaf spring is included as a component of the suspension. The uniquely designed leaf spring includes a relatively stiff front cantilever portion and a relatively soft rear cantilever portion. The front to rear cantilever stiffness ratio for a leaf spring of the present invention is preferably at least four to one or at least seven to one. To achieve this relatively high ratio, the leaf spring is designed so that the front cantilever is considerably thicker and shorter than the rear cantilever.
Axle suspension systems may be classified as having two general forms. A first form of axle suspension systems does not require auxiliary roll stabilizers because it utilizes leaf springs, coil springs and/or air springs which have a high vertical spring rate. The high vertical spring rate, however, provides for relatively uncomfortable riding conditions. A second form of axle suspension systems utilizes leaf springs, coil springs and/or air springs which have a soft vertical spring rate. Although this second form of axle suspension systems provides for relatively comfortable riding conditions, it generally lacks sufficient roll stability. The use of auxiliary roll stabilizers in such systems is often necessary, which increases the total cost and weight of these suspension systems. Based on the foregoing, it is desirable to provide a suspension system which, first, has sufficient roll stability such that the use of auxiliary roll stabilizers is unnecessary and, second, provides for relatively comfortable riding conditions for the vehicle.